Abstract:
Cryptococcus is a genus of saprophytic fungi with global distribution. Two species complexes, C. neoformans and C. gattii, pose health risks to humans and animals. Cryptococcal infections result from inhalation of aerosolized spores and/or desiccated yeasts from terrestrial reservoirs such as soil, trees, and avian guano. More recently, C. gattii has been implicated in infections in marine mammals, suggesting that inhalation of liquid droplets or aerosols from the air-water interface is also an important, yet understudied, mode of respiratory exposure. Water transport has also been suggested to play a role in the spread of C. gattii from tropical to temperate environments. However, the dynamics of fungal survival, persistence, and transport via water have not been fully studied. The size of the cryptococcal capsule was previously shown to reduce cell density and increase buoyancy. Here, we demonstrate that cell buoyancy is also impacted by the salinity of the media in which cells are suspended, with formation of a halocline interface significantly slowing the rate of settling of cryptococcal cells through water, resulting in persistence of C. neoformans within 1 cm of the air-water interface for over 60 min and C. gattii for 4-6 h. Our data also showed that during culture in yeast peptone dextrose media (YPD), polysaccharide accumulating in the supernatant formed a raft that augmented buoyancy and further slowed settling of cryptococcal cells. These findings illustrate new mechanisms by which cryptococcal cells may persist in aquatic environments, with important implications for aqueous transport and pathogen exposure.
摘要:
隐球菌是全球分布的腐生真菌属。两种复合物,C.新生动物和C.gattii,对人类和动物构成健康风险。隐球菌感染是由于吸入来自陆地水库如土壤的雾化孢子和/或干燥酵母而引起的,树木,和鸟粪.最近,C.gattii与海洋哺乳动物的感染有关,这表明从空气-水界面吸入液滴或气溶胶也很重要,然而研究不足,呼吸暴露模式。还建议水运在C.gattii从热带环境向温带环境的传播中起作用。然而,真菌存活的动态,持久性,水路运输尚未得到充分研究。先前已显示隐球菌胶囊的大小可降低细胞密度并增加浮力。这里,我们证明了细胞浮力也受到细胞悬浮培养基的盐度的影响,随着卤层界面的形成显着减慢隐球菌细胞通过水的沉降速率,导致在空气-水界面的1厘米内持续超过60分钟,C.gattii持续4-6小时。我们的数据还表明,在酵母蛋白胨葡萄糖培养基(YPD)中培养期间,积累在上清液中的多糖形成了一个筏子,增加了浮力并进一步减缓了隐球菌细胞的沉降。这些发现说明了隐球菌细胞可能在水生环境中持续存在的新机制,对水性运输和病原体暴露具有重要意义。
隐球菌病是一种导致全球发病率和死亡率的主要真菌病。C.新型真菌是公共卫生关注的主要真菌物种,导致免疫功能低下患者的机会性全身感染。C.gattii传统上是一种热带病原体,但在1990年代出现在不列颠哥伦比亚省和美国西北太平洋的温带气候中。这些地区的爆发也导致了自由放养鲸目动物隐球菌病的第一个宿主记录。C.gattii是特别值得关注作为一种新兴的真菌病原体,由于其能力引起临床疾病的免疫能力的患者,它最近传播到一个新的生态位,以及它对抗真菌疗法的较高抗性。我们的研究定义了影响隐球菌通过水的运输及其在空气-水界面的持久性的特征,这提高了我们对隐球菌水性运输和持久性机制的理解。